The Cell Cycle and Cancer

The Cell Cycle

• Cells go through a series of stages through their life

• These series of stages is called the cell cycle

• Each time the cell divides, the cell cycle starts over for the new cells

The Stages of the Cell Cycle1. G1 (Gap/growth 1)

Phase – The cell grows

2. S (synthesis) Phase – DNA is synthesized or duplicated

3. G2 (Gap 2) Phase – DNA is checked for errors; the cell grows more.

4. M (mitotic) Phase – Mitosis occurs

Cell Cycle Checkpoints

• At each checkpoint, a chemical messenger tells the cell whether it can go on to the next phase.

• If it does not get that message, it stays in that phase

Compare the cycle to a toll road, the check points to the toll booths and the chemical messengers to money.

2. Chemical Signals tell a cell when to start and stop dividing.

The Chemical Messengers may come from other cells or the cell’s own DNA

1.Before a cell divides, the DNA is checked to make sure it has replicated correctly. (If DNA does not copy itself correctly, a gene mutation occurs.

Neighboring cells communicate with dividing cells to regulate their growth also.

They may release the necessary chemical messengers for the others cells.

Cancer: What happens when something goes wrong?

Cancer is a disease of the cell cycle. Some of the body’s cells divide uncontrollably and tumors form.

Tumors in Liver

Tumor in Colon

DNA mutations disrupt the cell cycle.

Mutations may be caused by:

1. radiation 2. smoking 3. Pollutants 4. chemicals 5. viruses

While normal cells will stop dividing if there is a mutation in the DNA, cancer cells will continue

to divide with mutation.

Due to DNA mutations, cancer cells ignore the chemical signals that start and stop the cell cycle.

Due to DNA mutations, cancer cells cannot communicate with neighboring cells. Cells

continue to grow and form tumors.

Skin cancer

SUMMARY

Normal Cell Division

1. DNA is replicated properly.

2. Chemical signals start and stop the cell cycle.

3. Cells communicate with each other so they don’t become overcrowded.

Cancer Cells

1. Mutations occur in the DNA when it is replicated.

2. Chemical signals that start and stop the cell cycle are ignored.

3. Cells do not communicate with each other and tumors form.

Treating Cancers

Cancer treatments include drugs that can stop cancer cells from dividing.

Parts of a chromosome

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